A few families took a trip to an amusement park together. Tickets cost $$8.50$ each for adults and $$4.50$ each for kids, and the group paid $$70.00$ in total. There were $4$ fewer adults than kids in the group. Find the number of adults and kids on the trip.
Explanation: Let $x$ equal the number of adults and $y$ equal the number of kids. The system of equations is then: ${8.5x+4.5y = 70}$ ${x = y-4}$ Solve for $x$ and $y$ using substitution. Since $x$ has already been solved for, substitute ${y-4}$ for $x$ in the first equation. ${8.5}{(y-4)}{+ 4.5y = 70}$ Simplify and solve for $y$ $ 8.5y-34 + 4.5y = 70 $ $ 13y-34 = 70 $ $ 13y = 104 $ $ y = \dfrac{104}{13} $ ${y = 8}$ Now that you know ${y = 8}$ , plug it back into ${x = y-4}$ to find $x$ ${x = }{(8)}{ - 4}$ ${x = 4}$ You can also plug ${y = 8}$ into ${8.5x+4.5y = 70}$ and get the same answer for $x$ ${8.5x + 4.5}{(8)}{= 70}$ ${x = 4}$ There were $4$ adults and $8$ kids.